Oxidation of alkyl aromatic compounds

ABSTRACT

Alkyl aromatic compounds, and particularly alkyl aromatic hydrocarbons, are oxidized by treating with an oxygen-containing gas in the presence of a catalyst comprising a thalliumcontaining compound to form oxygenated aromatic compounds.

United States Patent Field .of Search ..260/524 R, 592, 599, 618 C QMassie 1 Mar. 27, 1973 [s41 OXIDATION OF ALKYL AROMATIC Pn'maryExaminer-Henry R. Jiles CQWOUNDS Assistant ExaminerR. S. Weissberg [75]Inventor: Stephen N. Massie, Palatine, Ill. 2:23? James Hoatson andRaymond [73] Assignee: Universal Oil Products Company,

Des Plaines, Ill. [57] ABSTRACT v [22] Filed: Dec. 28, 1970 Alkylaromatic compounds, and paiticularly alkyl aro- [211 App. N 0: 102,054matic hydrocar bons, are oxidized by treating with an oxygen-containinggas in the presence of a catalyst comprising a thallium-containingcompound to form [52] US. Cl ..260/524 R, 260/592, 260/599, oxygenatedaromatic compounds,

' 260/618 C .51' I t. Cl. ....C0 7c 47/54, C07c 49/78, C07c 63/02 9Claims N0 Drawings OXIDATION OF ALKYL AROMATIC COMPOUNDS SPECIFICATIONThis invention relates to a process for preparing oxygenated aromaticcompounds by treating an alkyl aromatic compound with anoxygen-containing gas in the presence of certain catalytic compositionsof matter of a type hereinafter set forth in greater detail.

Oxygenated aromatic compounds constitute an important class of chemicalcompounds which are useful for a variety of purposes. For example,benzaldehyde is useful in organic synthesis, especially for dyes and dyeintermediates. In addition it is also useful as a solvent for oils,resins, some cellulose ethers, cellulose acetate and cellulose nitrate.Other uses for this compound will include use in flavoring compounds, inthe production of synthetic perfumes, in the manufacture of cinnamicacid, in toilet preparations and soaps, in photographic chemicals, inbaking chemicals and in medicine. Benzoic acid which is anotheroxidation product prepared by the process of this invention is used as amordant in calico printing, it is also used in seasoning tobacco andimproving the aroma, in flavoring perfumes, in dentifrices in medicinesas a germacide, in textiles, in dye, as a plasticizer and resinintermediate, etc. Another product of the process of this inventioncomprises benzyl alcohol which is used as a solvent in perfumery andflavoring materials, as an intermediate in preparing other benzyl estersand ethers, as a high boiling solvent in cellulose derivativesproduction and also as a solvent for cellulose esters and ethers.Another use for this compound includes the use in resins, lacquer, filmsand in paint and varnish removers.

It is therefore an object of this invention to providea process for theoxidation of alkyl substituted aromatic compounds.

A further object of this invention is to provide a process for preparingoxygenated aromatic compounds utilizing alkyl substituted aromatichydrocarbons as the starting material. 7

In one aspect an embodiment of this invention resides in a process forthe oxidation of an alkyl substituted aromatic hydrocarbon whichcomprises treat-v ing said'alkyl substituted aromatic hydrocarbon withan oxygen-containing gas in the presence of a homogeneous catalystcomprising a thalliumcontaining compound at oxidation conditions, andrecovering the resultant oxygenated aromatic compound.

A specific embodiment of this invention resides in the process for thepreparation of oxygenated aromatic compounds which comprises treatingtoluene with air in the presence of thallium benzoate at a temperaturein the range of from about 100 to about 250C. and a pressure in therange of from atmospheric to about 100 atmospheres, and recovering theresultant benzyl alcohol, benzaldehyde, and benzoic acid.

Other objects and embodiments will be found in the following furtherdetailed description of the present invention.

As hereinbefore set forth, the present invention is concerned with theprocess for the oxygenation of alkyl substituted aromatic compounds, andparticularly alkyl substituted aromatic hydrocarbons to prepare thecorresponding flrst, second and third stage oxygenation products namely,the corresponding alcohols, aldehydes, and acids. The oxygenation iseffected in the presence of certain catalytic compositions of mattercomprising thallium-containing compounds. That the use of athallium-containing compound as a catalyst in the oxygenation of alkylsubstituted aromatic hydrocarbons would be effective is unexpected, inview of the fact that thallium is a member of Group lllA of the PeriodicTable and it is known that aluminum-containing compounds are ineffectiveoxidation catalysts. Examples of alkyl substituted aromatic compoundswhich may undergo oxidation to form the corresponding alcohols,aldehydes and acids will include both monoand polyalkyl substitutedaromatic hydrocarbons such as toluene, ethylbenzene, n-propylbenzene,n-butylbenzene, n-amylbenzene, o-xylene, m-xylene, p-xylene,o-diethylbenzene, m-diethylbenzene, p-diethylbenzene, o-dipropylbenzene,m-dipropylbenzene, pdipropylbenzene, mesitylene, pseudocumene,hemimellitene, durene, isodurene, prehnitene, pentamethylbenzene,hexamethylbenzene, etc.; l-methylnaphthalene, 2-methylnaphthalene,l-ethylnaphthalene, 2-ethylnaphthalene, l-n-propylnaphthalene,2-n-propylnaphthalene, lmethylanthracene, 2-methylanthracene, 1-

ethylanthracene, 2-ethylanthracene, etc. It is to be understood that theaforementioned alkyl substituted aromatic hydrocarbons are onlyrepresentative of the class of compounds which may be utilized as astarting material, and that the present invention is not necessarilylimited thereto.

Oxidation reaction conditions under which the process of the presentinvention is effected will include elevated temperatures, preferably ina range of from about to about 250C. and a pressure ranging fromatmospheric up to about 100 atmospheres or more. The oxidation agentwhich is utilized to prepare the desired product will comprise anoxygen-containing gas such as air or oxygen, the former constituting thepreferred oxidation agent due to the greater availability and lowercost. A

As hereinbefore set forth, the oxidation reaction is effected in thepresence of a catalyst comprising a thallium-containing compound. In thepreferred embodiment of the invention, the thallium-containing compoundwill comprise a compound which is homogeneous with the alkyl substitutedaromatic hydrocarbon undergoing oxygenation. Some specific examples ofthese homogeneous thallium-containing compounds will include the saltsof thallium and preferably the salts of organic acids such as aceticacid, propionic acid, butyric acid, valeric acid, caproic acid, hexanoicacid, caprylic acid, 2-ethylhexanoic acid, capric acid, cyclohexanoicacid, benzoic acid, toluic acid, etc., said salts being thalliumacetate, thallium propionate, thallium butyrate, thallium valerate,thallium caproate, thallium heptylate, thallium caprylate, thalliumcyclohexylate, thallium benzoate, thallium toluoate, etc. It is to beunderstood that the aforementioned thallium-containing compounds areonly representative of the class of compounds which may be used and thatthe present invention is not necessarily limited thereto. In addition,it is also contemplated that thallium salts of some inorganic acidswhich are homogeneous with respect to the starting materials may beused, although not necessarily with equivalent results, said saltsincluding thallous bromide, thallium tribromide, thallous chloride,thallium trichloride, thallous iodide, thallium triiodide, etc.

The process of this invention may be effected in any suitable manner andmay comprise either a batch or continuous type operation. For example,when a batch type operation is used, a quantity of the starting materialcomprising the alkyl substituted aromatic hydrocarbon is placed in anappropriate apparatus which may comprise a flask, or if superatmosphericpressures are to be employed, an autoclave of the rotating or mixingtype. In addition, the apparatus will also contain thethallium-containing catalyst. Following this, the oxidation agentcomprising an oxygen-containing gas is charged to the reactor which isthereafter heated to the mmols of benzoic acid, 33 mmols of benzaldehyde and 4 mmols of benzyl alcohol per mol of oxygen charged to thereactor.

EXAMPLE I] In this example 60 g. of ethylbenzene and 2 g. of thalliumbenzoate are placed in the glass liner of a rotating autoclave. Theautoclaveis thereafter sealed and air desired operating temperature.Upon completion of the predetermined residence time which may range fromabout 0.5 up to about 20 hoursor more in duration, heating isdiscontinued, the apparatus is allowed to return to room temperatureand, if at superatmospheric pressures, the excess pressure isdischarged. The reactionmixture is recovered from the apparatus andsubjected to conventional means of purification which will includewashing, drying, extraction, fractional distillation, etc., whereby-thedesired oxygenated products comprising alcohols, aldehydes, and acidsare recovered and separated.

It is also contemplated within the scope of this invention that theprocess may be effected in a continuous manner of operation. When such atype of operation is used, the alkyl substituted aromatic hydrocarbon iscontinuously charged to the reaction vessel which is maintained at theproper operating conditions of temperature and pressure. Thethallium-containing catalyst may, if so desired, be charged with thealkyl aromatic hydrocarbon inasmuch as said catalyst is homogeneous withrespect to the starting material and may be dissolved thereinalnaddition, the oxidation agent comprising an oxygen-containing gas suchas air or oxygen is also continuously charged to the reactor. Uponcompletion of the desired residence time, the reactor effluent iscontinuously discharged and'subjected'to separation means of the typehereinbefore set forth whereby the desired oxygenated productscomprising aromatic alcohols, acids, and aldehydes are recovered, whileany unreacted starting materials and catalysts are recycled to thereaction zone toform a portion of the feed stock.

The following examples are given to illustrate the process of thepresent invention which, however, are not intended to limit'thegenerally broad scope of the present invention in strict accordancetherewith.

EXAMPLE I In this example 60 g. of toluene and 2 g. ofa catalystcomprising thallium ben zoate were placed in the glass liner of arotating autoclave. The autoclave was sealed and air pressed in untilaninitial pressure of 35 atmospheres was reached. The autoclave was thenheated to a temperature of 180C. and maintained thereat for a period of16 hours, during which time the maximum pressure rose to 58 atmospheres.At the end of this time, heating was discontinued and the autoclaveallowed to return to room temperature, the final pressure at roomtemperature being 30 atmospheres. The excess pressure was discharged andthe autoclave was opened. The reaction mixture was recovered andsubjected to a gas-liquid chromatographic analysis, the oxidized productcomprising 247 pressed in until an initial pressure of 35 atmospheres isreached. The autoclave is then heated to a temperature of 180C. andmaintained thereat for a period of l6 hours, the maximum pressure atthis temperature reaching about 60 atmospheres. At the end of theaforementioned 16 hour period, heating is discontinued and the autoclaveis allowed to return to room temperature. The excess pressure isdischarged, the autoclave is opened and the reaction mixture isrecovered therefrom. Analysis of the product by means of a gasliquidchromatograph will disclose the presence of amethylbenzyl alcohol,acetophenone, and benzoic acid, the latter being the predominantproduct.

EXAMPLE III A charge comprising 60 g. of p-xylene, and 2 g. of thalliumacetate is placed in the glass liner of a rotating autoclave which isthereafter sealed. Oxygen is then pressed in until an initial pressureof 25 atmospheres is reached, and the autoclave is then heated to atemperature of l80'C. After maintaining the autoclave at thistemperature for a period of 16 hours, during which time the maximumpressure will rise to about 60 atmospheres, heating is discontinued andthe autoclave is allowed to return to room temperature. The excesspressure'is then discharged, the autoclave is opened and the reactionmixture is recovered. Analysis of the mixture by means of a gas-liquidchromatograph utilizing methyl ester derivatives of the carboxylic acidswill disclose the presence of 4-methylbenzyl alcohol, 4-rnethylbenzaldehyde, 4-methylbenzoic acid,'and 1,4- benzenedicarboxylicacid.

EXAMPLE IV A charge stock consisting of 60 g. of mesitylene and 2 g. ofthallium benzoate catalyst is placed in the glass liner of a rotatingautoclave which is thereafter sealed. Airis pressed in until an initialoperating pressure of 35 atmospheres'is reached and the autoclave isheated to a temperature of 200C. After maintaining the autoclave at thistemperature for a period of 16 hours, heating is discontinued and theautoclave isallowed to return to .room temperature. The excess pressureis then ture in the range of from about l00 to about 250C. and apressure in the range of from about atmospheric to about 100atmospheres, and recovering the resultant oxygenated aromatic compound.

2. The process as set forth in claim 1 in which said oxygen containinggas is oxygen.

3. The process as set forth in claim 1 in which said oxygen containinggas is air.

4. The process as set forth in claim 1 in which said thallium containingcompound is thallium benzoate.

5. The process as set forth in claim 1 in which said thallium containingcompound is thallium acetate.

6. The process as set forth in claim 1 in which said alkyl aromatichydrocarbon is toluene and said oxygenated alkyl aromatic compounds arebenzyl alcohol, benzaldehyde and benzoic acid.

7. The process as set forth in claim 1 in which said alkyl aromatichydrocarbon is ethylbenzene and said oxygenated alkyl aromatic compoundsare a-methylbenzyl alcohol, acetophenone and benzoic acid.

8. The process as set forth in claim 1 inwhich said alkyl aromatichydrocarbon is p-xylene and said oxygenated alkyl aromatic compounds are4-methylbenzyl alcohol, 4-methylbenzaldehyde, 4-methylbenzoic acid and1,4-benzenedicarboxylic acid.

9. The process as set forth in claim 1 in which said alkyl aromatichydrocarbon is mesitylene and said oxygenated alkyl aromatic compoundsare 3,5 -dimethylbenzyl alcohol; 3,S-dimethyIbenZaldehyde, 3,5-dimethylbenzoic acid, S-methyl-l,3-benzenedicarboxylic acid andl,3,5-benzenetricarboxylic acid.

2. The process as set forth in claim 1 in which said oxygen containinggas is oxygen.
 3. The process as set forth in claim 1 in which saidoxygen containing gas is air.
 4. The process as set forth in claim 1 inwhich said thallium containing compound is thallium benzoate.
 5. Theprocess as set forth in claim 1 in which said thallium containingcompound is thallium acetate.
 6. The process as set forth in claim 1 inwhich said alkyl aromatic hydrocarbon is toluene and said oxygenatedalkyl aromatic compounds are benzyl alcohol, benzaldehyde and benzoicacid.
 7. The process as set forth in claim 1 in which said alkylaromatic hydrocarbon is ethylbenzene and said oxygenated alkyl aromaticcompounds are Alpha -methylbenzyl alcohol, acetophenone and benzoicacid.
 8. The process as set forth in claim 1 in which said alkylaromatic hydrocarbon is p-xylene and said oxygenated alkyl aromaticcompounds are 4-methylbenzyl alcohol, 4-methylbenzaldehyde,4-methylbenzoic acid and 1,4-benzenedicarboxylic acid.
 9. The process asset forth in claim 1 in which said alkyl aromatic hydrocarbon ismesitylene and said oxygenated alkyl aromatic compounds are3,5-dimethylbenzyl alcohol, 3,5-dimethylbenzaldehyde,3,5-dimethylbenzoic acid, 5-methyl-1,3-benzenedicarboxylic acid and1,3,5-benzenetricarboxylic acid.